A recent societal trend calls for more employees to work from home or other sites that are remote from the corporate office. This is achieved via remote access to data networks.
The traditional way remote employees accessed the corporate network is via Long Distance dial to a remote access server in the corporate data center. Such remote access server or local call server is a device that answers incoming phone calls with racks of modems, authenticates users as authorized data users (not hackers) and hands data queries to the corporate network. Dozens or even hundreds of remote users or workers may almost simultaneously dial in to dozens or hundreds of modems, in one remote access server.
Internet Service Providers are now setting up Internet Protocol IP access in remote access server nodes all over the world. The IP network can give them a great way to provide access to remote users.
The traditional approach takes bursty data traffic and it carries it on Constant Bit Rate telephone calls circuits for such a long distance—usually all the way to corporate headquarters. This explains why they are quite expensive. And the bursty traffic inefficiently uses the circuit bandwidth, because there are often long periods of silence. In contrary, the Internet Service Provider ISP remote access service can be more efficient because ISP carries the data call on a circuit for only a short distance—the local phone call distance between the remote user and a remote access server in a local office. The remote access server will terminate the circuits of multiple users, multiplex the bursty data efficiently into one packet stream, and conserve long distance circuits. This last service for support of remote and mobile employees is often named Dial Internet Protocol, Virtual Private Dial Networking, or simply remote access.
An example of a software supporting such remote access is given by the product called Windows NT 4.0 Remote Access from Microsoft. With Windows NT remote access, remote access clients connect to remote access servers and are transparently connected to the remote access server, known as point-to-point remote access connectivity. Alternately, they are transparently connected to the network to which the remote access server is attached, known as point-to-LAN remote access connectivity. This transparent connection allows remote access clients to dial-in from remote locations and access resources as if they were physically attached to the network.
That software product provides two different types of remote access connectivity:
(i) Dial-up remote access, where a remote access client uses via the telecommunications infrastructure to create a temporary physical circuit or a virtual circuit to a port on a remote access server. Once the physical or virtual circuit is created, the rest of the connection parameters can be negotiated.
(ii) Virtual private network remote access where a client uses an IP network to create a virtual point-to-point connection with a remote access server acting as the virtual private network server. Once the virtual point-to-point connection is created, the rest of the connection parameters can be negotiated.
Nowadays, voice-over-IP (VOIP) starts to be of enough good quality that enterprise customers move to implement Voice-over-IP networks. It is directly related to the hope to decrease the costs associated with maintaining multiple networks and increase productivity as new applications are brought to market extending the application of voice communication. Voice-over-IP enables carrying voice traffic (for example, telephone calls and faxes) over an IP network. This support is implemented using voice packet technology. In voice-over-IP, the digital signal processor segments the voice signal into frames and stores them in voice packets. These voice packets are transported using IP in compliance with one or several signaling specifications. But when an enterprise network provides IP telephony service, it must be able to support so called Emergency Calling Service ECS also known in the US and Canada as E911. Indeed the enterprise network must have the capability of determining the user's location and call back number, routing the call to the appropriate Public Safety Answering Point PSAP, and conveying the location and call back information to that PSAP.
For an enterprise IP network to properly support ECS, it must achieve the following:                Identify the location of ECS user and dispatch help to the correct location within a limited time;        Connect the ECS call to the appropriate PSAP jurisdiction. The correct PSAP is usually the one nearest the user;        Location information provide correct emergency location information number of the ECS user so that the PSAP can dispatch help to the correct location;        Call back information provide the correct number for calling back the ECS user in case the call is disconnected.        
The key to supporting the first three requirements is enterprise network determination of the user's location, regardless of the terminal access scenario.